ISSN 0008-3194 (p)/ISSN 1715-6181 (e)/2019/126–138/$2.00/©JCCA 2019

Suspected neuropathy causing persistent idiopathic facial : a report of four cases Nicholas Moser, BSc, DC, FCCS(C)1 Brad Muir, HBSc(Kin), DC, FRCCSS(C)2

Persistent idiopathic facial pain is often a disabling La douleur faciale idiopathique persistante est souvent condition for patients. Due to a lack of agreed upon une condition invalidante pour les patients. En raison de diagnostic criteria and varied symptomatology, the l’absence de critères diagnostiques convenus et d’une diagnosis of persistent idiopathic facial pain is elusive symptomatologie variée, le diagnostic de douleur faciale and remains one of exclusion. It is typically described as idiopathique persistante est difficile à établir et demeure a unilateral, deep, poorly localized pain in the territory un diagnostic d’exclusion. On décrit généralement of the trigeminal nerve, however there are a number of la douleur comme étant unilatérale, profonde et mal case reports that describe bilateral symptoms. Unlike localisée dans la région du nerf trijumeau, mais il existe trigeminal , the condition encompasses a wider un certain nombre de rapports de cas qui décrivent des distribution that does not conform or relate to a specific symptômes bilatéraux. Contrairement à la névralgie dermatome. In addition, the pain is typically continuous, faciale, l’affection englobe une distribution plus with no periods of remission and there are no signs or large qui n’est pas conforme ou liée à un dermatome symptoms suggestive of autonomic involvement. Reports précis. De plus, la douleur est généralement continue, documenting the response to various conservative sans période de rémission et il n’y a aucun signe ou treatments for persistent idiopathic facial pain have been symptôme suggérant une atteinte du système nerveux widely variable likely due to the heterogeneity of the autonome. Les rapports documentant la réponse à condition. Four cases of persistent idiopathic facial pain divers traitements conservateurs utilisés pour la douleur faciale idiopathique persistante ont été très variables, probablement en raison de l’hétérogénéité de l’affection. Quatre cas de douleur faciale idiopathique persistante due à un soupçon de neuropathie du nerf trijumeau et

1 Private practice, Oakville, Ontario 2 Canadian Memorial Chiropractic College

Corresponding author: Brad Muir, 6100 Leslie Street, Toronto, ON M2H 3J1 Tel: (416) 482-2340 E-mail: [email protected] © JCCA 2019

The authors have no disclaimers, competing interests, or sources of support or funding to report in the preparation of this manuscript. The involved patients provided consent for case publication.

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due to suspected trigeminal nerve neuropathy and their leur prise en charge sont présentés. Dans les quatre management are presented. A specific form of targeted, cas décrits, une forme spécifique de thérapie par manual, instrument-assisted, intra-oral vibration therapy vibration ciblée, intraorale, manuelle, appuyée par des appeared to provide relief in the four cases described. instruments, a semblé apporter un soulagement.

(JACC. 2019;63(2):126-138) (JCCA. 2019;63(2):126-138) mots clés : nerf trijumeau1, douleur faciale, key words : trigeminal nerve1, facial pain, chiropratique, thérapie par vibration, douleur faciale chiropractic, vibration therapy, atypique.

Introduction with PPTTN defined as “spontaneous or touch evoked Lifetime prevalence of non-specific facial pain is esti- pain predominantly affecting the receptive field of one mated at 26%.1 The condition presents as a diagnostic or more divisions of the trigeminal nerve. The duration challenge for even the most experienced clinicians due to ranges widely from episodic (minutes to days) and may its multifaceted presentation and etiology. also be constant. The pain tends to spread with time and Persistent idiopathic facial pain (PIFP) is typically is mostly unilateral without crossing the midline.”11 (pg 50) described as deep, poorly localized pain in the territory They also suggest that the pain develops within three of the trigeminal nerve. It is most often unilateral, how- months of an identifiable trauma and lasts for more than 3 ever approximately one-third of patients develop bilat- months.11 eral symptoms.2 PIFP often spreads to a wider area, not The purpose of this article is to familiarize the clin- conforming to a specific dermatome. In addition, the pain ician with the clinical presentation, diagnosis, etiology is typically continuous with no periods of remission and and management of PIFP secondary to trigeminal nerve there are no signs or symptoms of autonomic involve- neuropathy as currently understood. Four cases are pre- ment.2 Recent evidence supports the notion that PIFP may sented to illustrate the features of the disorder. itself be a condition.2, 3-7 Friedman et al.8 demonstrated consistent maxillary alveolar tenderness Case presentations (MAT) in the distribution of the on the in- volved side of the face in patients diagnosed with atypical Case 1 facial pain. The authors state that this tenderness is often A 28-year old female employed as a full-time medic- incorrectly attributed to lateral pterygoid hypertonicity or al receptionist presented to a chiropractic clinic with a spasm, despite the inaccessibility of this muscle to digital 1.5-year history of bilateral facial pain located over the palpation.8 They found intra-oral tenderness in the max- temporal and temporomandibular joint regions. The onset illary molar periapical area in over 90% of asymptomatic was attributed having a “nerve struck” while undergoing patients, with laterality and degree of tenderness extensive dental work for caries. Subsequently, a root closely related to symptoms.9 Significant ipsi- canal and a dental crown were required. The pain over the lateral tenderness and increased local temperature was temporomandibular region was described as an intermit- found in the maxillary molar periapical area on palpation tent dull ache. The temporal headache pain was described bilaterally during unilateral migraine, tension type head- as a constant squeezing and pressure sensation occurring aches, and facial pain.10 weekly. Both painful areas were rated at seven out of 10 Neuropathic pain secondary to trigeminal nerve injury on the numerical rating scale (NRS). The major aggravat- has also been poorly defined in the literature.11 Benoliel et ing factor was clenching. The pain was worse in the mor- al.11 has proposed a modified diagnostic criteria for per- ning and after work. The patient denied any lancinating, ipheral painful traumatic trigeminal neuropathy (PPTTN) burning or paroxysmal sensations in the face and denied

J Can Chiropr Assoc 2019; 63(2) 127 Suspected trigeminal nerve neuropathy causing persistent idiopathic facial pain: a report of four cases

Figure 1. Location of the infraorbital and supraorbital foramen. The infraorbital foramen is the exit point of the infraorbital nerve from the skull (red dot indicated by the blue arrow). By pinching the skin over the eyebrow Figure 2. directly over the pupillary line (with midline gaze), the Proposed trigeminal nerve tension test. Palpating the supraorbital foramen (or notch) can be easily palpated supraorbital nerve just superior to the supraorbital and subsequently the supraorbital nerve (indicated by foramen (or notch) (red arrow) the patient is asked to the red arrow). The location of the pupil (white dot) is open their mouth. An increase in tension and/or pain indicated by the grey arrow. would indicate a positive test.

any associated nausea, vomiting, photophobia, phono- of the right temporomandibular joint (TMJ). There was phobia and auras. At baseline, her Jaw Functional Limit- moderate tenderness over the temporalis, masseter and ation Scale score was zero, indicating no limitations. The medial pterygoid muscles bilaterally. Palpation over the Jaw Functional Limitation Scale has demonstrated good infraorbital and supraorbital foramen, the exit point from reliability and construct validity in assessing limitations the skull of the infra (See Figure 1) and supraorbital (See in mastication, jaw mobility and verbal and emotional ex- Figure 1) nerves, respectively, elicited tenderness, which pression.12 increased on mouth opening (See Figure 2) recreating a On examination, the patient weighed 54 kg and stood lesser version of her temporal headache pain. Intra-oral 163 cm tall. Active and passive ranges of motion of the palpation along the superior mucobuccal fold in the area cervical spine were full and pain free. Orthopaedic testing of the superior alveolar nerve and inferior mucobuccal of the cervical spine, inclusive of Spurling’s and Jack- fold at the exit and distribution of the mental nerve, the son’s, was unremarkable. The cervical paraspinal muscu- terminal branch of the inferior alveolar nerve, was locally lature was diffusely tender, however no pain referred to tender bilaterally reproducing her presenting symptoms. the areas of the chief complaint. A rightward C-shaped Examination of other and peripheral nerv- shift of the mandible was visualized during jaw open- ous system was within normal limits. ing but no obvious clicking was noted. A palpable clunk An MRI, ordered by her family medical doctor, of both was noted bilaterally upon closing the mouth. No lock- temporomandibular joints (TM) demonstrated “a normal ing was reported or visualized. Incisal opening, using a left TMJ. The right TMJ meniscus was anteriorly sub- Therabite ROM scale13, measured 53mm, with left lateral luxed in the resting/neutral position but reduced on open- mandibular deviation measuring 15mm and right lat- ing. There was no abnormality of configuration or signal eral mandibular deviation measuring 10mm. There was change within the condylar head or glenoid surface of the a restriction noted during posterior-anterior joint play TMJ.”

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full-time student presented to a chiropractic clinic with a seven-year history of bilateral and a three- year history of recurrent neck pain. The patient reported the onset of pain overlying the TMJ began when she was 17-years old after her orthodontic braces were removed. The pain persisted and was made worse during a standard dental procedure. The pain was rated at a constant four out of 10 throughout the day. The pain was described as a dull ache with consistent referral of pain to the temporal, frontal and supraorbital regions of the head. Eating large pieces of food, requiring her to open her mouth wide, aggravated the pain. In addition, chewing gum and the use of a store bought mouth guard also exacerbated her symptoms. The patient received treatment intermittently directed to the TMJ for her jaw and headache symptoms Figure 3. from a chiropractor over a period of several years. These Locating the supratrochlear foramen (red arrow). treatments consisted of cervical spinal manipulative ther- By pinching the skin over the eyebrow directly over apy, soft-tissue therapy to the cervical and facial muscu- the inner canthus, the supratrochlear foramen can be lature and intra-oral vibration-assisted therapy directed at easily palpated and subsequently the supratrochlear the muscles of mastication. She reported the treatments nerve. provided temporary relief of the headache pain but had improved opening and closing of her jaw considerably. The patient felt her neck pain was due to poor postures A diagnosis of persistent idiopathic facial pain second- while attending school. The pain was located bilaterally ary to trigeminal nerve neuropathy, tension type head- at the base of the neck extending to the postero-lateral aches and temporomandibular disorder (TMD) was made. shoulders bilaterally. The pain was described as a dull The plan of management consisted of mobilizations to the ache and rated at an average of 4 out 10. The pain was TMJ bilaterally, soft-tissue therapy to the affected cervic- made worse by prolonged studying at a desk. The patient al and orofacial musculature and intra-oral vibration-as- denied any upper extremity pain referral or paraesthesia. sisted soft-tissue therapy directed to the affected muscles On examination, the patient weighed 62 kg and stood of mastication and the superior and inferior mucobuccal 155 cm tall. Active and passive ranges of motion of the fold in the area of the superior alveolar and mental nerves cervical spine were full and pain free. Spurling’s and (see management section for further description of treat- Jackson’s tests were unremarkable. The cervical posterior ment procedure). paraspinal musculature was tender, however there was no After 10 treatments over a 12-week period, the pa- pain referred to the areas of the TM complaint. A right- tient reported significant improvement in their headache sided deviation on opening of the mouth was visualized. and jaw pain. She reported experiencing less than one No jaw locking was seen on examination or reported by headache per month at 5-month follow-up. She reported the patient. Incisal opening, using a Therabite ROM scale, a complete resolution of the pain located over the tem- measured 37mm. Palpation intraorally along the superior poromandibular region. Follow-up at 5 months revealed mucobuccal fold in the area of the superior alveolar nerve that her jaw remained symptom free, but she continued and inferior mucobuccal fold at the exit and distribution to have occasional mild headache pain, as previously de- of the mental nerve was locally tender as were the mus- scribed. cles of mastication bilaterally. There was tenderness over the supraorbital (Figure 1) and supratrochlear (Figure 3) Case 2 foramina, bilaterally and increased with mouth opening A 24-year old female employed as a part-time cashier and (See Figure 2). At baseline her Jaw Functional Limitation

J Can Chiropr Assoc 2019; 63(2) 129 Suspected trigeminal nerve neuropathy causing persistent idiopathic facial pain: a report of four cases

Scale score was 17. Cranial nerves and peripheral nervous cervical spine were full and pain free. Spurling’s and system examination was otherwise within normal limits. Jackson’s test were unremarkable. The posterior cervic- A diagnosis of persistent idiopathic facial pain sec- al paraspinal musculature was tender, however there was ondary to trigeminal nerve neuropathy and TMD was no to the areas of the TM complaint. Open- made on the basis of the clinical assessment. The plan ing and closing the mouth revealed a non-painful audible of management consisted of mobilizations to the TMJ bi- clicking in the bilateral TMJ. Incisal opening, using the laterally, soft-tissue therapy to the affected cervical and Therabite ROM scale, measured 38mm, with left lateral orofacial musculature and intra-oral vibration-assisted mandibular deviation measuring 10mm and right lateral soft-tissue therapy directed to the affected muscles of mandibular deviation measuring 11mm. Maximal open- mastication and the superior and inferior mucobuccal ing caused pain along the left TMJ. Restriction during fold in the area of the superior alveolar and mental nerves anterior-posterior joint play of bilateral TMJ was noted. (refer to management section for further description of Palpation intraorally of the muscles of mastication and treatment procedure). along the superior mucobuccal fold in the area of the su- The patient reported a complete resolution of her perior alveolar nerve elicited tenderess bilaterally. Pal- orofacial pain after seven treatments over a seven-week pation over the supraorbital foramen (or notch) (Figure period. Follow-up at three-months revealed that she had 1), was tender bilaterally, increasing with mouth opening remained symptom free. (See Figure 2). Examination of the cranial nerves and per- ipheral nervous system was within normal limits. Case 3 A diagnosis of persistent idiopathic facial pain second- A 25-year old female full-time student presented to a chiro- ary to trigeminal nerve neuropathy and TMD was made. practic clinic with a five-year history of bilateral jaw pain The plan of management consisted of mobilizations to the and . The jaw pain and headaches reportedly TMJ bilaterally, soft-tissue therapy to the affected cervic- began shortly after prolonged dental work. The headaches al and orofacial musculature and intra-oral vibration-as- were described as a daily dull ache located over the tem- sisted soft-tissue therapy directed to the affected muscles poral regions. The patient denied any nausea, vomiting, of mastication and the superior and inferior mucobuccal photophobia, phonophobia, or auras. Prolonged studying, fold in the area of the superior alveolar and mental nerves. sitting and/or driving aggravated the headache pain. Self- The patient reported a significant improvement in her directed, extra-oral massage of the TMJ muscles reported- headache and jaw pain. After 20 treatments over a nine- ly decreased the intensity of the headaches. The jaw pain week period the patient reported having less than one was described as dull and achy and rated three to four out headache per month and intermittent, two out of 10 jaw of 10 on an NRS. Teeth grinding and not wearing her night- pain intensity. Follow-up at eight-months revealed that time mouth guard, prescribed by her dentist, increased the the improvement had been maintained. The patient is cur- TMJ pain. The patient described a non-painful clicking rently receiving ongoing symptomatic care for her inter- on opening and closing the jaw. The patient denied any mittent low-grade jaw pain and headaches. lancinating or paroxysmal pain. At baseline her Jaw Func- tional Limitation Scale score was 25. The patient reported Case 4 receiving ongoing treatments at intermittent frequency A 63-year old female retired florist presented to a chiro- directed to the TMJ for her jaw and headache symptoms practic office with a three-month history of left jaw pain. from a chiropractor for a period of several years. Her treat- No headaches were reported. The jaw pain reportedly ments consisted of cervical and facial soft-tissue therapy began shortly after a dental crown procedure. The patient and intra-oral vibration-assisted therapy directed at the described the pain as a constant dull ache; however, she muscles of mastication. She reported the treatments pro- noted that up to three times per week she experienced vided only temporary relief of the headache pain but had sharp, shooting pain along the left mandible from the angle improved her jaw function considerably. of the mandible toward the mental foramen. The jaw pain On examination, the patient weighed 70 kg and stood was rated at a daily four to five out of 10 on an NRS with 155 cm tall. Active and passive ranges of motion of the episodes of sharp, shooting pain reaching eight out of 10.

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Aggravating factors for the jaw pain included eating large revealed no pain since her last visit. The patient continued mouthfuls of hard foods, such as apples, and talking and to receive ongoing supportive care as above. moving her tongue in side-to-side movements. At baseline her Jaw Functional Limitation Scale score was zero. Discussion On examination, the patient weighed 79.4 kg and stood The applicability of understanding this complex anatomy 152.4 cm tall. Active and passive ranges of motion of the for clinicians who utilize intra-oral digital palpation as cervical spine were within normal limits. Spurling’s and part of their assessments cannot be overstated. Under nor- Jackson’s were unremarkable. The cervical paraspinal mal circumstances, tissues overlying peripheral nerves musculature was tender, however there was no pain re- are painless to gentle palpation, however, when neural ferred to the areas of the TM complaint. No audible click tissue is inflamed even gentle palpation can cause focal or deviation was noted during maximal jaw opening. In- and referred pain.14, 15 cisal opening, utilizing the three finger test, was full (three Given the complexity of trigeminal nerve neuroanat- fingers) and pain free. Palpation intraorally along the omy and its’ numerous connections, dysfunction and/or superior mucobuccal fold in the area of the superior al- injury can result in a myriad of symptoms, some of which veolar nerve and inferior mucobuccal fold at the exit and will be discussed below. (See Appendix 1 for a more thor- distribution of the mental nerve revealed local tenderness ough discussion of the anatomy of the trigeminal nerve). on the left side more so than the right. Palpation of the inferior mucobuccal fold in the area of the exit and dis- Pathophysiology of nerve injury tribution of the mental nerve reproduced the chief com- is a blanket term used to describe plaint. Palpation over the supraorbital (See Figure 1) and disorders affecting the function of one or more peripheral supratrochlear (See Figure 3) foramina was unremark- nerves due to numerous causes including trauma, disease able bilaterally. Palpation of the temporalis muscle was or dysfunction.16 Within the nerve sheath, the blood nerve nontender, however, palpation intra and extra-orally of barrier is vital to ensure homeostasis. Breakdown of the all other accessible muscles of mastication were focally barrier can occur with a nerve injury, including compres- tender. Examination of the cranial nerves and peripheral sion and tension injuries.17 Secondary to breakdown of nervous system was within normal limits. the barrier, is a loss of homeostasis within the endoneural A diagnosis of persistent idiopathic facial pain sec- environment.17 This results in the accumulation of vari- ondary to trigeminal nerve neuropathy and trigeminal ous proteins as well as infiltration by lymphocytes, fibro- neuralgia was made. The plan of management consisted blasts, and macrophages as a reaction to previously pro- of facial acupuncture, low level laser therapy (LLLT) to tected antigens contained within the perineurial space.18, 19 the TM joint, soft-tissue therapy to the affected cervical There is thus the potential for a mini-compartment syn- and orofacial musculature, and intra-oral vibration-as- drome within the fascicles due to the build up of fluid.18 sisted soft-tissue therapy directed to the affected muscles The tortuous arrangement of the fascicles in the periph- of mastication and the superior and inferior mucobuccal eral nerves embedded in its fibrous matrix is predisposed fold in the area of the superior alveolar and mental nerves to the mechanical propagation of this neurogenically in- bilaterally. The patient had had success with both LLLT duced local compartment syndrome.18 The neurogenically and acupuncture for previous cervical and upper thoracic induced inflammation provides a cytokine-based -mech musculoskeletal complaints so it was included in the plan anism for a cycle of inflammation without frank demyel- of management. ination. This helps to explain the inconclusive and often The patient reported a significant improvement in her normal findings found on electrophysiological studies or jaw pain after her first treatment. After six treatments over other imaging modalities in disorders where patients re- a six-week period the patient reported having a minimal port paraesthesia, such as in , thor- amount of pain and very few episodes of shooting pain. acic outlet syndrome and atypical facial pain.18 The patient also received a custom-made mouthguard Relatively recent diagnostic ultrasound work has dem- from her dentist three weeks into treatment, which she onstrated that affected nerves show a significantly in- felt also helped her jaw pain. Follow-up at three-months creased cross-sectional area compared to the asymptomatic

J Can Chiropr Assoc 2019; 63(2) 131 Suspected trigeminal nerve neuropathy causing persistent idiopathic facial pain: a report of four cases

side.20 Kara et al.20 showed an increase in the cause of both nerve trunk pain and dysesthetic pain which in those patients with low and unilateral sciatica. may be caused by persistent inflammation in the nerve.27 Cartwright et al.19 reported similar findings in the median Bove states, “symptoms can appear as local tenderness nerve in unilateral carpal tunnel syndrome, as did Cho et of the nerve (nerve trunk pain), or a ‘doorbell’ type of al.21 in unilateral with the greater occipi- response, where palpation leads to dysesthetic symptoms tal nerve. It would stand to reason that an inflamed nerve in a more distal region.”27 Cranial nerves are known to be would be predisposed to a greater number of entrapment richly innervated by nervi nervorum.28 sites along its route due to an increase in cross-sectional The neurogenic inflammation, causing an irritation area and thus a greater proximity to surrounding soft tissue. within the nerve sheath, leads to the cascade of swell- Support for the hypothesis that an inflamed nerve is ing, cellular recruitment and spread of perineural and en- more predisposed to compression has come from the re- doneural fibrosis, and provides a possible explanation for sults of decompression procedures.22 Direct observation the enigmatic clinical presentation of persistent idiopathic of the scalene triangle during such procedures has demon- facial pain. This mechanism helps explain the finding of strated fibrous bands and persistent adhesions that can be pain on palpation of the various branches of the trigeminal visualized to limit normal movement of the brachial plex- nerve in the presented cases and also the lack of sensory us.22 Small perineural adhesions are said to be responsible findings (numbness or tingling) or motor deficits (weak- for the continued symptom formation and, as noted, are ness or atrophy). difficult to visualize with current imaging techniques. Re- section of the perineural adhesions normalizes blood flow Diagnosis and results in the resolution of distal vasospasms as con- Atypical facial pain or more commonly referred to as, per- firmed thermographically.22 Ellis17 reported that more than sistent idiopathic facial pain (PIFP) is typically described 100 surgical decompressive cases utilizing intraoperative as deep, poorly localized pain in the territory of the thermography documenting the presence of both directly trigeminal nerve. It is most often unilateral, however ap- mechanical (fibrous bands and fibrotically transformed proximately one-third of patients develop bilateral symp- muscles) and neurogenic (small perineural adhesions) toms.2 Unlike , PIFP often spreads mechanisms for neural constriction, inflammation and to a wider area, not conforming to a specific dermatome. distal vasospasm. Evidence of similar pathophysiology In addition, the pain is typically continuous with no per- has been documented for ulnar and entrap- iods of remission and there are no signs or symptoms of ments. Rosenbaum et al., concluded that the presence of autonomic involvement. Apart from sensitivity to palpa- endoneural fibrosis was the most damaging due to the dir- tion and tension along the course of the nerve, as dem- ect effect on nerves and blood vessels.23 onstrated in our four cases, the condition shows no other Upton and McComas24 introduced the concept of the abnormal findings in clinical examination or additional double crush phenomenon in the early 1970’s. They stated investigations and as a result, the diagnosis of PIFP is one that a proximal nerve injury might predispose distal sites to of exclusion.2 compression and that the opposite, reverse double crush, Currently there is a lack of diagnostic criteria and was also a possibility. Upton and McComas24 noted that validated diagnostic procedures. However, the Inter- compression along the nerve alters axoplasmic flow, which national Headache Society (IHS) describes PIFP as per- subsequently leads to pathology and symptomatology. sistent facial and/or oral pain, with varying presentations These changes have been demonstrated in animal mod- but recurring daily for more than two hours per day over els.24 Although most authors agree it is more of a “multiple more than three months, in the absence of clinical neuro- crush” presentation25, this is an important concept clinical- logical deficits.28 In addition, IHS suggests the following ly as the failure to recognize and treat the multiple points of diagnostic criteria: injury will likely result in an unsuccessful outcome. – facial and/or oral pain that is recurring daily for Sauer et al.26 showed that the nervi nervorum provide greater than two hours per day for greater than innervation to the nerve sheath in peripheral nerves and three months; are nociceptive in nature. The nervi nervorum may be the – the pain is characterized as being poorly local-

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ized, not following the distribution of a periph- toms there were no abnormalities with elec- eral nerve; trophysiological or QST testing.5 – the character of pain is either dull, aching, or Forssell et al.2 sought to elucidate the pathophysiology nagging. of atypical facial pain and test the idea that the disorder – In addition, the clinical neurological examination represents a clinically undiagnosed neuropathic pain con- is normal and the pain cannot be attributed to any dition through the use of clinical, neurophysiologic and known or understood pathological process.28 thermal QST. They examined atypical facial pain pa- Recent evidence supports the notion that PIFP may itself tients and patients with diagnosed trigeminal neuropathic be a neuropathic pain condition.2, 3-7 Friedman et al.8 demon- pain. The majority (75%) of atypical facial pain patients strated consistent maxillary alveolar tenderness (MAT) in showed abnormalities in electrophysiological or thermal the distribution of the maxillary nerve on the involved side QST recordings or both. It would appear that PIFP is a of the face in patients diagnosed with atypical facial pain. heterogeneous entity, which is better understood as a dis- The authors state that this tenderness is often incorrectly at- order that forms a spectrum of neuropathic involvement tributed to lateral pterygoid hypertonicity or spasm, despite due to the amount of inflammation present. being inaccessible to digital palpation.8 Preliminary data of Due to the relative lack of a gold standard in diagnos- intra-oral tenderness in the maxillary molar periapical area ing trigeminal neuropathic pain, the suspected diagnosis was noted in over 90% of asymptomatic migraine patients, of PIFP secondary to trigeminal neuropathy may best be with laterality and degree of tenderness closely related to facilitated with palpation and proposed nerve tensioning headache symptoms.9 On palpation bilaterally during uni- (i.e. mouth opening). Ellis17 states that the inflammation, lateral migraine, tension type headaches, and facial pain, if not identified and treated appropriately, can spread both the maxillary molar periapical area displayed significant perineurally (within the nerve) and endoneurally causing ipsilateral tenderness and increased local temperature.10 As activation of the CNS. A study done by Younger et al.29 previously stated, local neural inflammation can result in showed changes in the gray matter in several areas of the symptom provocation to normally non-noxious palpation.15 brain in patients with TMD versus controls on MRI. The In this example, tissues surrounding the jaw supplied by authors reported these changes were likely associated terminal branches of the maxillary nerve are sensitized sec- with dysregulation of the trigeminal and limbic systems ondary to neural inflammation. as well as somatotopic reorganization in the putamen, In order to improve the accuracy of detecting subclinical thalamus and somatosensory cortex29. The mechanism cranial neuropathies, sensitive neurophysiological record- outlined by Ellis can then cause the subsequent inflam- ing and quantitative sensory testing (QST) have been rec- mation of other adjacent/connected nerves, and can lead ommended. Jääskeläinen et al.5 examined whether elec- to mirror symptoms in the opposite limb.17 With respect trophysiological testing of trigemino-facial system could to the four cases outlined above, this could be the mech- aid in the diagnosis of atypical facial pain. They found that anism involved in the tenderness of several branches of atypical facial pain patients could be divided into three the trigeminal nerve accessible to palpation including the groups based on their electrophysiological findings: supratrochlear, supraorbital, infraorbital, the muscular 1. major trigeminal neuropathy, representing branches to the muscles of mastication and the superi- the patients that had both clinical and electro- or alveolar and mental nerves that may occur bilaterally physiological signs of trigeminal neuropathy even with a unilateral complaint. despite normal brain magnetic resonance im- Therefore, tenderness of the nerves branches would aging (MRI); suggest inflammation along the route of the trigeminal 2. minor trigeminal neuropathy, where the pa- nerve with an element of central sensitization. It can be tients displayed increased excitability dur- difficult to be confident that the nerve is being palpated ing electrophysiological testing signifying especially when other structures in the area could be the trigeminal nerve dysfunction despite normal source of pain. Increasing pain with palpation of the nerve MRI; and under tension especially with no other soft tissue structure 3. idiopathic, where despite the clinical symp- crossing the tensioned structure would reinforce that the

J Can Chiropr Assoc 2019; 63(2) 133 Suspected trigeminal nerve neuropathy causing persistent idiopathic facial pain: a report of four cases

palpated tissue is in fact the nerve. In cases 1, 2 and 3 there was tenderness over the supraorbital nerve branch that increased under the tension position of mouth open- ing. This position would theoretically create tension in the trigeminal nerve due to a stretch of the inferior alveolar branch, in particular the mental nerve, with opening. To our knowledge, this proposed trigeminal nerve tension test has not previously been described in the literature.

Management Secondary to the concept of increased tenderness and temperature being signs of inflammation, Friedmanet al.9 examined the efficacy of intra-oral chilling for the relief of headache pain. A randomized controlled study design was used to evaluate the effectiveness of maxillary intra- Figure 4. oral chilling (MIC) in 35 symptomatic episodic migraine Depiction of palpation and treatment of the left mental patients compared to oral sumatriptan and sham (tongue) nerve using targeted vibration therapy. Acupuncture chilling. Pain and nausea was recorded at baseline, one, points are targeting (from left to right to midline) two, four and 24 hours after the treatment. Both MIC (p= Gallbladder 1, the right supraorbital foramen (exit 0.001) and sumatriptan (p= 0.024) significantly reduced of the supraorbital nerve), Urinary Bladder 2 – right the pain scores compared to control group. No significant supratrochlear foramen (exit of supratrochlear nerve), differences between MIC and sumatriptan were noted.9 and Extra 3 (Yintang). Of interest, the sumatriptan caused mild side effects, in- cluding dizziness, paraesthesia, and somnolence, in seven of 12 subjects. Only one in 12 subjects for the MIC group the symptomatic side(s) was significant (p<0.001) in re- reported a minor side effect, which included dizziness and ducing headaches with minimal side effects.30 post-treatment gingival tenderness. In addition to the conservative treatments outlined Friedman et al.30 also investigated the effectiveness above, a targeted manual instrumented assisted intra-oral and tolerability of topical nonsteroidal anti-inflammatory vibration therapy has demonstrated effectiveness (See drugs (NSAID) to treat headache patients. Topical medi- Figures 4 and 5)31. Targeted vibration therapy is hypoth- cation was applied to the periapical area of the maxillary esised to aid in the breakdown of scar tissue and mobilize molars on the symptomatic side(s) in 20 chronic head- the surrounding soft-tissues32, increase local blood flow33 ache patients. Patients recorded the frequency, severity, and reportedly, to decrease pain.34, 35 Kerschan-Schindl et duration, and type of headache for 60 days. After 30 days al.33 demonstrated a significant increase in blood volume the patients were instructed on how to apply the medica- and mean blood flow after three-minutes of vibration ex- tion and told to apply the once daily for 30 ercise in the quadriceps and gastrocnemius muscles. The days. The patient reported headache burden was exam- suggested mechanism of action of vibration therapy is to ined, which was defined as the average headache inten- reduce blood viscosity and improve blood flow velocity.33 sity (0 to 10 scale), multiplied by its duration in hours. Intra-oral vibration therapy theoretically disrupts the pro- The authors noted that the average headache burden score posed dynamic occurring within the trigeminal decreased from 454.8 (baseline 30 days) to 86.5 (during nerve in patients with PIFP via mobilizing the nerve itself the 30 day treatment phase).30 The reported side effects and surrounding soft-tissues, as well as promoting im- were minor and included one incident of gastrointestin- proved local circulation. al intolerance, one incident of burning gingiva, and one It is important to note, however, that a lack of a clear incident of cheek irritation. They concluded that NSAID pathophysiological basis makes it difficult to establish a applied to the periapical area of the maxillary molars on validated/evidence-based treatment protocol. Given the

134 J Can Chiropr Assoc 2019; 63(2) N Moser, B Muir

titioner managing persistent facial pain. If suspected, ap- propriate referral and investigations should be pursued prior to the commencement of the treatments proposed above or if the clinical picture fails to resolve in a reason- able amount of time.

References 1. Macfarlane TV, Blinkhorn AS, Davies RM, Kincey J, Worthington HV. Oro-facial pain in the community: prevalence and associated impact. Community Dent Oral Epidemiol. 2002;30(1):52-60. 2. Forssell H, Tenovuo O, Silvoniemi P, Jääskeläinen SK. Differences and similarities between atypical facial pain and trigeminal neuropathic pain. . 2007;69(14):1451-1459. Figure 5. 3. Lang E, Kaltenhäuser M, Seidler S, Mattenklodt P, Neundörfer B. Persistent idiopathic facial pain exists Depiction of palpation of the left superior mucobuccal independent of somatosensory input from the painful fold in the area adjacent to the left superior alveolar region: findings from quantitative sensory functions and nerve. somatotopy of the primary somatosensory cortex. Pain. 2005;118(1-2):80-91. 4. Benoliel R, Gaul C. Persistent idiopathic facial pain. Cephalalgia. 2017;37(7):680-691. psychosocial comorbidities that accompany 5. Jääskeläinen SK, Forssell H and Tenovuo O. conditions and the lack of randomized controlled trials Electrophysiological testing of the trigeminofacial for the putative diagnosis, a pragmatic multidisciplinary system: aid in the diagnosis of atypical facial pain. Pain. approach is recommended. Since the application of vibra- 1999;80:191–200. tory stimulation has been shown to increase local blood 6. Derbyshire SW, Jones AK, Devani P, Friston KJ, flow33 and decrease pain34, 35, it may be reasonable to as- Feinmann C, Harris M, Pearce S, Watson JD, Frackowiak RS. Cerebral responses to pain in patients sume that targeted vibration therapy may be an effective with atypical facial pain measured by positron intervention in the treatment of the suggested dynamic emission tomography. J Neurol Neurosurg Psychiatry. ischemia in the terminal branches of the trigeminal nerve. 1994;57(10):1166-1172. 7. Hagelberg N, Forssell H, Aalto S. Altered dopamine Summary D2 receptor binding in atypical facial pain. Pain. 2003;106:43–48. Four cases of PIFP due to suspected trigeminal nerve 8. Friedman MH. Atypical facial pain: the consistency neuropathy and their conservative management are de- of ipsilateral. Maxillary area tenderness and elevated scribed. Studies have postulated that in patients with temperature. J Am Dent Assoc. 1995;126(7):855-860. PIFP there is local pathology (inflammation) of the dis- 9. Friedman MH. Local inflammation as a mediator tal branches of the trigeminal nerve, which results in the of migraine and tension-type headache. Headache. range of symptoms described. Empirically, the use of 2004;44(8):767-771. 10. Friedman MH, Luque AF, Larsen EA. Ipsilateral intraoral specific manual release techniques (soft tissue therapy), tenderness and increased local tenderness and elevated and the use of a hand held apparatus that transmits vi- temperature during unilateral migraine and tension-type brations might be useful. At this time, PIFP thought to be headache. Headache Q. 1997;8: 341-344. due to trigeminal nerve neuropathy remains a diagnosis 11. Benoliel R, Zadik Y, Eliav E, Sharav Y. Peripheral painful of exclusion. Awareness of other sinister conditions that traumatic trigeminal neuropathy: clinical features in 91 cases and proposal of novel diagnostic criteria. J Orofacial may mimic PIFP such as, giant cell arteritis, septic arth- Pain. 2012; 26(1): 55. ritis/ of the TMJ, tumors and pseudo-tumours of 12. Ohrbach R, Larsson P, List T. The jaw functional limitation the TMJ as well as common etiological conditions with scale: development, reliability, and validity of 8-item and accepted standard treatments is imperative for the prac- 20-item versions. J Orofac Pain. 2008;22(3):219-230.

J Can Chiropr Assoc 2019; 63(2) 135 Suspected trigeminal nerve neuropathy causing persistent idiopathic facial pain: a report of four cases

13. Saund DS, Pearson D, Dietrich T. Reliability and validity myofascial temporomandibular pain is associated with of self-assessment of mouth opening: a validation study. neural abnormalities in the trigeminal and limbic systems. BMC Oral Health. 2012;12:48. PAIN®. 2010 May 1;149(2):222-228. 14. Hall T, Quintner J. Responses to mechanical stimulation 30. Friedman MH, Peterson SJ, Frishman WH, Behar CF. of the upper limb in painful cervical . Aust Intraoral topical nonsteroidal antiinflammatory drug J Physiother. 1996;42(4):277-285. application for headache prevention. Heart Dis. 15. Walsh J, Hall T. Reliability, validity and diagnostic 2002;4(4):212-215. accuracy of palpation of the sciatic, tibial and common 31. Muir B, Brown C, Brown T, Tatlow D, Buhay J. peroneal nerves in the examination of low back related leg Immediate changes in temporomandibular joint opening pain. Man Ther. 2009;14(6):623-629. and pain following vibration therapy: a feasibility pilot 16. Misra UK, Kalita J, Nair PP. Diagnostic approach study. J Can Chiropr Assoc. 2014;58(4): 467-480. to peripheral neuropathy. Ann Ind Acad Neurol. 32. Macintyre I, Kazemi M. Treatment of posttraumatic 2008;11(2):89. arthrofibrosis of the radioulnar joint with vibration 17. Ellis W. as a disorder of therapy (VMTX Vibromax TherapeuticsTM): A case report neurogenic inflammation. Vasc Endovasc Surg. 2006;40: and narrative review of literature. J Can Chiropr Assoc. 251-244. 2008;52(1):14-23. 18. Snell R. Clinical Neuroanatomy. Philadelphia: Wolters 33. Kerschan-Schindl K, Grampp S, Resch H, Henk C, Kluwer Health/Lippincott Williams & Wilkins, 2010:345. Preisinger E, Fialka-Moser V, Imhof H. Whole-body 19. Cartwright MS, Hobson-Webb LD, Boon AJ, Alter KE, vibration exercise leads to alterations in muscle blood Hunt CH, et al. Evidence-based guideline: neuromuscular volume. Clin Physiol. 2001; 21(3):377–382. ultrasound for the diagnosis of carpal tunnel syndrome. 34. Melzack R. From the gate to the matrix. Pain. 1999; Muscle Nerve. 2012; 46(2): 287-293. 6(S12). 20. Kara M, Levent O, Tiftik T, Kaymak B, Ozel S, Akkus S, 35. Falempin M, Fodili In-Albon S. Influence of brief et al. Sonographic evaluation of sciatic nerves in patients daily tendon vibration on rats soleus muscle in non- with unilateral sciatica. Arch Phys Med Rehabil. 2012; weightbearing situation. J Appl Physiol. 1999;87(1):3–9. 93(9): 1598-1602. 36. Netter FH. Atlas of Human Anatomy. 6th ed. Philadelphia: 21. Cho JC, Haun DW, Kettner NW. Sonographic evaluation Elsevier, 2014. of the greater occipital nerve in unilateral occipital 37. Moore KL, Dalley AF. Clinically oriented anatomy. 5th. neuralgia. J Ultrasound Med. 2012; 31(1): 37-42. ed. Philadelphia: Lippincott Williams & Wilkins, 2006: 22. Cheng S, Ellis W, Stoney R. Thoracic outlet syndrome: 918, 939-45, 1131, 1139-142. Supraclavicular approach. Vascular surgery. 5th. ed. 38. Schünke M, Schulte E and Schumacher U.Thieme Atlas Boston: Springer, 1994: 475-82. of Anatomy. Head and Neuroanatomy. Stuttgart: Thieme, 23. Rosenbaum R, Ochoa J. Acute and chronic mechanical 2007: 75-77. nerve injury: Pathologic, physiologic and clinical 39. Fallucco M, Janis JE, Hagan RR. The anatomical correlations. Carpal tunnel syndrome and other disorders morphology of the supraorbital notch: clinical relevance of the median nerve. Boston: Butterworth-Heinemann, to the surgical treatment of migraine headaches. Plastic 1993:197-230. Resconstruct Surg. 2012;130(6): 1227-1233. 24. Upton AM, Mccomas A. The double crush in nerve- 40. Janis JE, Hatef DA, Hagan R, Schaub T, Liu JH, entrapment syndromes. Lancet. 1973; 302(7825):359-362. Thakar H, Bolden KM, Heller JB, Kurkjian TJ. Anatomy 25. Mackinnon SE. Pathophysiology of nerve compression. of the supratrochlear nerve: implications for the surgical Hand Clin. 2002;18(2):231-41. treatment of migraine headaches. Plast Resconstruct Surg. 26. Sauer SK, Bove GM, Averbeck B, Reeh PW. Rat 2013;131(4):743-750. peripheral nerve components release calcitonin gene- 41. Janis JE, Ghavami A, Lemmon JA, Leedy JE, Guyuron B. related peptide and E 2 in response to The anatomy of the corrugator supercilii muscle: noxious stimuli: evidence that nervi nervorum are Part II. Supraorbital nerve branching patterns. Plastic nociceptors. Neuroscience. 1999;92(1):319-325. Resconstruct. Surg. 2008;121(1):233-240. 27. Bove GM. Epi-perineurial anatomy, innervation, and 42. Norton N. Netter’s Head and Neck Anatomy for Dentistry. axonal nociceptive mechanisms. J Bodyw Mov Ther. 2nd. ed. Philadelphia: Saunders. 2012. 2008;12:185-190. 43. Johnstone DR, Templeton M. The feasibility of 28. Headache Classification Committee of the International palpating the lateral pterygoid muscle. J Prosthet Dent. Headache Society (IHS). The International Classification 1980;44(3):318-323. of Headache Disorders, 3rd. ed (beta version). Cephalalgia. 44. Friedman MH. Local inflammation as a mediator 2013;33(9):629-808. of migraine and tension-type headache. Headache. 29. Younger JW, Shen YF, Goddard G, Mackey SC. Chronic 2004;44(8):767-771.

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Appendix 1. Anatomy review of the trigeminal nerve

The trigeminal nerve is the second largest cranial nerve orbital nerve further branches into a superficial and deep in the body.36,37 The nerve is enveloped by a connective branch. The deep branch runs deep to the frontalis muscle tissue called the mesoneurium, which is critical to allow in a superior direction supplying sensation to the fron- gliding during movement.36,37 The mesoneurium is con- toparietal scalp. The superficial branch further divides tinuous with the external epineurium, which defines and with some divisions either penetrating or passing over the surrounds the nerve trunk. The nerve trunk is composed of frontalis muscle as it travels superiorly to supply sensa- myelinated and unmyelinated nerve fibres bound together tion to the forehead and anterior scalp.41 within fascicles, which are surrounded by the perineur- CN V2 exits the cranium via the foramen rotundum ium.36 In between the fascicles is the internal epineurium. and enters the pterygopalatine fossa and divides into the Finally, the connective tissue within the matrix of the fas- zygomatic nerve, ganglionic branches to the pterygopal- cicle is termed the endoneurium.36 atine ganglion and infraorbital nerve.36, 38 CN V2 supplies The trigeminal nerve supplies both general somatic af- sensation to the skin of the face over the maxilla, includ- ferent and special visceral efferent to derivatives of the ing the upper lip, maxillary teeth, mucosa of the nose, first pharyngeal arch.36,37 It is comprised of four nuclei, maxillary sinuses, and palate, as well as the dura matter three sensory and one motor. of the anterior part of the middle cranial fossa.36, 38 The composition of the sensory root is predominant- The infraorbital nerve passes through the inferior orbit- ly pseudounipolar neurons that make up the trigeminal al fissure to enter the infraorbital canal and exits onto the ganglion. The , housed within a dural face via the infraorbital foramen (See Figure 1).42 Its fine recess lateral to the cavernous sinus, receives afferent and terminal branches supply the skin between the lower eye- efferent information from the peripheral ganglionic neur- lid and upper lip. The anterior superior alveolar branches, ons forming the three nerve divisions: ophthalmic (CN middle superior alveolar branches and posterior superi- V1), maxillary (CN V2), and mandibular (CN V3).36, 38 or alveolar branches are the other terminal branches and CN V1 exits the cranium via the superior orbital fis- form the superior dental plexus, which supplies sensory sure and provides the afferent supply to the skin, mucosa innervation to the maxillary teeth.38 These three branches membranes and conjunctiva of the front of the head and are often the targets for nerve blocks during dental pro- nose as well as the anterior and supratentorial dura mat- cedures.42 Since there are numerous overlying structures er.36, 38 The first branch from the ophthalmic division is in this area, including medial and lateral pterygoid mus- the small recurrent meningeal branch, which supplies the cles, a structurally accurate diagnosis cannot be made sensory innervation to the . The ophthalmic through palpation alone. However, sensitivity in this area division divides into three branches the names of which suggests local inflammation, which may be inclusive of indicate the structures innervated: lacrimal nerve, frontal the posterior superior alveolar nerve.43, 44 nerve and nasociliary nerve.38 The frontal nerve further Unlike the other two branches, CN V3 has both gener- branches into the supratrochlear and supraorbital nerves al sensory and branchial motor components. The mixed that exit the skull from their similarly named foramina. afferent-efferent mandibular division exits the cranium Fallucco et al. report that only 26.7% of the cadavers in through the foramen ovale and enters the infratemporal their study had a supraorbital foramen while 83.3% had fossa on the external aspect of the base of the skull.36, 38 a notch.39 In 10% of the cadavers there was both a fora- It gives off a meningeal branch, which re-enters the mid- men and a notch.39 In 86.0% of their cases with a notch, dle cranial fossa to supply sensory innervation to the the neurovascular bundle passing through was encased by dura.36, 38 The mandibular division has four main sensory fibrous bands suggesting a potential compression39 site. branches: auriculotemporal nerve, lingual nerve, inferior The supratrochlear nerve supplies sensation to the skin alveolar nerve, and buccal nerve. The branches of the aur- and soft tissue of the glabella, lower medial portions of iculotemporal nerve supply the temporomandibular joint, the forehead, upper eyelid and conjunctiva.40 The supra- the temporal skin, external auditory canal, and the tym-

J Can Chiropr Assoc 2019; 63(2) 137 Suspected trigeminal nerve neuropathy causing persistent idiopathic facial pain: a report of four cases

panic membrane. The lingual nerve supplies the sensory The efferent fibers of the inferior alveolar nerve sup- fibers to the anterior two-thirds of the tongue. The afferent ply the mylohyoid and the anterior belly of the digastric fibers of the inferior alveolar nerve pass through the man- muscles. The pure motor branches of the CN V3 leave the dibular foramen into the mandibular canal and branches main trunk distal to the origin of the meningeal branch into the inferior dental plexus, which supply the mandibu- and supply the masseter muscle (masseteric nerve), tem- lar teeth. The mental nerve, a terminal branch of the infer- poralis muscle (deep temporal nerve), pterygoid muscle ior alveolar nerve, supplies the skin of the chin, lower lip (pterygoid nerve), tensor tympani muscle (nerve of the and body of the mandible. The buccal nerve pierces the tensor tympani muscle) and tensor veli palatini muscle buccinators muscle and supplies sensation to the mucous (nerve of the tensor veli palatini muscle).36, 38 membrane of the cheek.36, 38

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